This invention relates to control of the intake fresh air amount of a supercharged engine.
Tokkai Hei 8-338256 published by the Japanese Patent Office in 1996 discloses feedback control of a supercharging pressure variation mechanism of a turbocharger of an engine to a target value.
This prior art technique detects the supercharging pressure or the intake fresh air amount of the intake passage of the engine, and controls the supercharging pressure variation mechanism so that the supercharging pressure or intake fresh air amount coincides with a target value determined according to a running condition.
The turbocharger comprises an exhaust gas turbine disposed in the exhaust passage of the engine, and a compressor driven by the exhaust gas turbine, compresses air and supplies it to the engine via the intake passage.
The supercharging pressure variation mechanism comprises a gate which varies the inflowpath cross-sectional area of exhaust gas led to the exhaust gas turbine.
This feedback control compensates scatter in the performance of a sensor for detecting the supercharging pressure and an actuator that drives the supercharging pressure variation mechanism.
However, there is a considerable response delay until the gate operation of the exhaust gas turbine disposed in the exhaust passage of the engine affects the fresh air amount actually aspirated by the engine. On the basis of such a response delay, it is difficult to set the gain of feedback control large.
It takes some time before scatter in the performance of the sensor or actuator is compensated and the fresh air amount settles to the target value.
The prior art technique therefore has a problem in that control error is large in the transient running state of the engine.
It is therefore an object of this invention to improve the fresh air amount control response of a supercharger.
In order to achieve the above object, this invention provides a control device for a supercharger of an engine. The supercharger is provided with a mechanism for adjusting an intake air amount of the engine according to a signal. The device comprises a sensor which detects a running state of the engine, a sensor which detects an intake air amount of the engine, and a controller.
The controller is functioning to set a target intake air amount of the engine based on the running state, calculate an operational target value of the intake air amount adjusting mechanism based on the target intake air amount, set an open loop control value of the signal based on the operational target value, calculate a feedback correction amount including an integral correction value of the signal to cause the intake air amount to coincide with the target intake air amount, calculate a learning value based on the integral correction value when the intake air amount coincides with the target intake air amount, modify the feedback correction amount to cause the sum of the learning value and the feedback correction amount to be constant, and output the signal determined based on the open loop control value, the learning value and a modified feedback correction amount to the intake air amount adjusting mechanism.
This invention also provides a control method of a supercharger of an engine. The supercharger comprising a mechanism for adjusting an intake air amount of the engine according to a signal. The method comprises detecting a running state of the engine, detecting an intake air amount of the engine, setting a target intake air amount of the engine based on the running state, calculating an operational target value of the intake air amount adjusting mechanism based on the target intake air amount, setting an open loop control value of the signal based on the operational target value, calculating a feedback correction amount including an integral correction value of the signal to cause the intake air amount to coincide with the target intake air amount, calculating a learning value based on the integral correction value when the intake air amount coincides with the target intake air amount, modifying the feedback correction amount to cause the sum of the learning value and the feedback correction amount to be constant, and outputting the signal determined based on the open loop control value, the learning value and a modified feedback correction amount to the mechanism.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.